The Stratigraphy and Surficial Geology of New Providence and Surrounding Islands, Bahamas

Abstract

Eight distinct rock units representing discrete high sea-level event s have been identified on New Providence (NPl) and surrounding islands. Each is distinguished by a unique set of physical, biological, and geochemical characteristics. At least three of these units are new to the stratigraphic column of NPI since the landmark study of Garrett and Gould in 1984. Others previously described have been further clarified. A map of the surficial geology of NPI shows the areal distribution of the major units. Based on the number and character of paleosol-bounded limestone parasequences, it appears that at least five interglacial cycles are distinguishable. Whole-rock amino acid racemization (AAR) ratios confirm the stratigraphic sequence, and indicate that isotope Stages 1 through 11 are most likely included among eight depositional packages: (Stage 1-2 events ; Stage 5-3 events; Stage 7- 1 event; Stage 9-1 event; Stage 11-1 event). Six interglacial units on NPI contain intertidal sedimentary facies and shoreline indicators from which a highstand curve has been derived. Of particular significance is the recognition of higher-than-present paleosea levels associated with three middle Pleistocene units.

Our findings indicate that the surficial geologic record of NPI is longer and more complex than previously thought , and that the northern Bahama Banks have experienced little if any subsidence over the past half-million years, based on the height of middle Pleistocene sea levels. The sea-level data from NPI and nearby islands have important implications for isotopic and tectonic coastline studies, and on the timing and effect of orbital parameters on sea-level and climate history during the late Quaternary.